Plugging means for melt system polymer lines

ABSTRACT

MEANS IS PROVIDED FOR PLUGGING ANY ONE OF A PLURALITY OF POLYMER DISTRIBUTION CONDUITS UPSTREAM OF AN ASSOCIATED METERING PUMP IN A MELT SYSTEM SO THAT THE PUMP MAY BE DISCONNECTED AND REPLACED WHENEVER NECESSARY WITHOUT INTERRUPTING OPERATION AT THE OTHER CONDUITS. THE PLUGGING MEANS PROVIDED INCLUDES A HEAT EXCHANGE STRUCTURE INSTALLED ON EACH OF THE DISTRIBUTION CONDUITS AND ARRANGED FOR SELECTIVE CIRCULATION OF COOLING FLUID THERETHROUGH TO SOLIDIFY POLYMER TEMPORARILY IN THE RELATED DISTRIBUTION CONDUIT AND THEREBY PLUG THE SAME WHENEVER DESIRED.

Nov. 23, 1971 J, H. BELL, JR, E'I'AL 3,621,526

PLUGGING MEANS FOR MELT SYSTEM POLYMER LINES Filed Sept. 10, 1969 3 Sheets-Shoot 1 F/GUPE lNVE/VTORS JOHN H. BELL, JR.

CHARLES S. W. KING By 4T7 R/VEYS Nov. 23, 1971 3,621,526

PLUGGING MEANS FOR MELT SYSTEM POLYMER LINES Filed Sept. 10, 1959 J. H. BELL, JR. ETAL 3 Sheets-Shoot 2 INVENTORS JOHN H. BELL CHARLES S. W.

JR. KING PM QMiL A TTOR/VEYS Nov. 23, 1971 3,621,526

PLUGGING MEANS FOR MELT SYSTEM POLYMER LINES J. H. BELL, JR. ETAL 3 Shoots-Shoot 3 Filed Sept. 10, 1969 FIGURE 3 FIGURE 5 4 /V VE N 70/95 JOHN H. BEL CHARLES S. W.

BY 2M Q 4 ATTORNEYS United States Patent O 3,621,526 PLIJGGING MEANS FOR MELT SYSTEM POLYMER LINES John H. Bell, .Ir., and Charles S. W. King, Charlotte,

N.C., assignors to R. H. Bouligny, Inc., Charlotte, NC. Filed Sept. 10, 1969, Ser. No. 856,719

Int. Cl. D01d 3/00 US. Cl. 18-8 1? 6 Claims ABSTRACT OF THE DISCLOSURE Means is provided for plugging any one of a plurality of polymer distribution conduits upstream of an associated metering pump in a melt system so that the pump may be disconnected and replaced whenever necessary without interrupting operation at the other conduits. The plugging means provided includes a heat exchange structure installed on each of the distribution conduits and arranged for selective circulation of cooling fluid therethrough to solidify polymer temporarily in the related distribution conduit and thereby plug the same whenever desired.

BACKGROUND OF THE INVENTION Because metering pumps provide an advantageous volumetric control of melted polymer being delivered to extrusion outlets, they are typically employed in melt spinning systems and are currently being included often in other melt systems, such as those adapted for producing monofil or slit film.

In melt spinning systems, melted filament forming polymer is commonly pressure-fed to the inlet of a spinning manifold in which a plurality of distribution conduits run from the inlet to respective metering pumps that deliver in turn to spinnerettes, or spin packs, forming polymer extrusion outlets at a plurality of spinning positions. There may be anywhere from four to thirtytwo spinning positions provided in a given system. When the number of spinning positions is large, half of them are often arranged in each of two spinning manifolds, and when this is done a distribution manifold may be additionally employed for initially dividing the melted polymer supply into separate streams for each spinning position before delivery to the spinning manifolds, particularly if continuous polymerization means is provided to supply the melted polymer.

In any event, the metering pumps are of the gear type and are individually powered for independent operation and control at each spinning position. Such independent operation and control allows any one of the metering pumps to be stopped whenever the components of the associated spin pack (i.e., the filter or the spinnerette) require cleaning or repair, as they frequently do.

However, whenever trouble develops at one of the metering pumps the entire spinning system must be shut down in order to deal with it, unless some provision is made to allow disconnection of the pump while the system otherwise continues to run. The pumps require maintenance attention less frequently than the spin packs, but they do, for example, spring leaks on occasion, or lock-up at times when foreign matter in the polymer feed cannot be passed, or simply wear enough over a period to run a spinning position off-denier, so that necessary correction of their operating condition is not uncommon.

If the spinning system must be shut down in order to deal with a defective metering pump, as much as twenty-four hours can be consumed in placing the system back on-stream after correcting the defect. Any attempt to alleviate the resulting production loss by equipping the polymer distribution conduits with valve means,

3,6Zl,526 Patented Nov. 23, 1971 ice that may be selectively operated to close only the conduit at which the defective pump must be disconnected, has the significant disadvantage of introducing a joint in the conduit at which it is a practical impossibility to avoid a degree of flow surface discontinuity sufiicient to induce polymer stagnation, with consequent film deposits that find their way into the polymer stream from time to time to cause objectionable filter clogging, even if they will pass the pump without damaging it. Comparable problems arise in dealing with any melt system that employs metering pumps.

The present invention makes it possible to avoid any flow surface interruption in the polymer distribution conduits of a melt system while at the same time providing for effective temporary plugging of any conduit at which a pump must be disconnected.

SUMMARY OF THE INVENTION The plugging means provided by the present invention disposes a heat exchange structure at each polymer distribution conduit through which cooling fluid can be circulated for solidifying a polymer plug in a particular distribution conduit and thereby stopping polymer flow therein when necessary.

The heat exchange structures are installed on the respective polymer distribution conduits with means for connecting them for circulation of cooling fluid therethrough so that each conduit plugging means constitutes a unit that may be employed selectively.

A preferred arrangement of the heat exchange structure is a coil of tubing. With such an arrangement it is also advantageous to provide a tubular shield over the tubing coil throughout its length to minimize condensation of the usual temperature-sustaining vapor thereat during operation of one of the plugging units.

Additionally, where the particular melt system involved employs a relatively high polymer feeding pressure, it is desirable to deform a portion of the polymer distribution conduits at the installed heat exchange structure of the plugging units so as to vary the cross sectional configuration of the conduits for mechanically holding solidified polymer against melted polymer feeding pressure thereon, rather than depending alone on frictionally lodging the solidified plug.

DESCRIPTION OF THE DRAWINGS 'FIG. 1 is a schematic diagram of a plugging means arranged according to the present invention in a typical melt spinning system;

FIG. 2 is a plan view of a representative four-position manifold assembly for a spinning system of the FIG. 1 type incorporating plugging units of the present invention for each position;

FIG. 3 is a section detail taken at the line 3-3 in FIG. 2;

FIG. 4 is a fragmentary detail of the FIG. 3 plugging unit modified to incorporate a covering shield at its coiled portion and having the associated polymer distribution conduit deformed adjacently; and

FIG. 5 is a section detail taken. at the line 55 in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 diagrams the arrangement of a plugging unit 10 embodying the present invention as installed in a manifold assembly 12 of a melt spinning system, in which the space within the manifold 12 is heated by circulation therethrough of a temperature-zsustaining vapor in the usual manner (as noted, for example, in US. Pat. No. 2,841,821). The melted polymer inlet is indicated at 14 with a distribution conduit 16 running therefrom to a side wall housing 18 at which a metering pump 20 is installed for controlling delivery of melted polymer through a discharge conduit 22 to a spin pack housed at 24 in the manifold bottom.

The plugging unit includes an anchor block 26 that is fixed in the top wall of the manifold 12 so as to be externally accessible and has two tubing legs 28 and 30 assembled therewith that extend within the manifold 12 to an intermediate heat exchange structure 32 installed on the distribution conduit 16 upstream of the pump 20. In the illustrated embodiment, the heat exchange structure 32 is formed by a coiled portion of continuous tubing that forms the two legs 28 and 30. Alternatively, the heat exchange structure 32 can be provided as a chamber surrounding the conduit 16 with the tubing legs 28 and 30 connected thereto and suitable flow bafiiing arranged interiorly thereof, although the illustrated coiled configuration of a tubing portion is simpler and is the preferred arrangement.

The anchor block 26 of the plugging unit 10 is bored to receive and have the tubing legs 28 and 30 fixed therein (see FIG. 3) and the resulting bores are tapped adjacent their outwardly opening ends (as indicated at 34 and 36 in FIG. 3) so as to be fitted externally of the manifold 12 for connection with cooling fluid supply and drain lines represented at 38 and 40 in FIG. 1.

Both lines 38 and 40 suitably consist of steam hose, with the supply line 38 running from a cooling fluid supply source, such as a water header at 42, through a shut-off valve 44 and a needle valve 46 for flow control to a connector fitting 48 suited for attachment to a similar fitting 50 installed at the tapped bore 34 of the plugging unit anchor block 26. In the illustrated embodiment, the connector fittings 48 and 50 are of the quick disconnect type, so that the supply line 38 may be attached and removed readily at any one of the plugging units 10 provided in the spinning system. Both connectors 48 and 50 should be of the sort that are fluid tight when disconnected so as to eliminate any spillage from the supply line or flash-back from the plugging unit 10 upon disconnection. The drain line 40 extends from the plugging unit 10 to any convenient drain facility 52, and is provided with a similar connector fitting 54 for paired attachment at the anchor block tapped bore 36 through a connector fitting 56 which should always be open so as to avoid trapping any cooling fluid in the plugging unit 10.

Operation of a particular plugging unit 10 is accomplished by paired connection of the supply and drain hoses 38 and 40 as indicated in FIG. 1 and opening of the shut-off valve 44 to admit cooling fluid, after which the needle valve 46 is adjusted to limit the fluid flow until only a small stream of fluid discharges into the drain 52. Once the fluid flow has started and been adjusted, about fifteen minutes is needed for solidification of a polymer plug in the distribution conduit 16 at the operable plugging unit 10. As soon as the plugging becomes evident, the defective metering pump 20 is simply removed and replaced while production continues at the other spinning positions.

Upon replacement of the pump 20, the shut-off valve 44 is closed to stop the flow of cooling fluid and the supply line 38 is removed. The drain line 40 is kept in place until all cooling fluid has vaporized from the plugging unit 10 and then it is also removed, following which the polymer plug will remelt in about fifteen minutes and the replaced pump 20 may be started, as soon as it is hot enough, to place the involved spinning position back in production.

A representative arrangement of a series of plugging units 10, 110, 210 and 310 in a typical four-position manifold 12 is shown in FIG. 2, the distribution conduits from the polymer inlet 14 being indicated by dotted lines at 16, 116, 216 and 316 with: the installed heat exchange portions of the plugging units likewise indicated in dotted lines at 32, 132, 232 and 332; the related metering pump housings at 18, 118, 218 and 318; the discharge conduits therefrom at 22, 122, 222, and 322; and the spin pack housings at 24, 124, 224, and 324. FIG. 3 further shows the arrangement of these elements in transverse section at the position of the plugging unit 10, and the arrangement for every other spinning position is essentially the same.

FIGS. 4 and 5 illustrate additional features that may be employed to advantage in the plugging means arrangement. First, if a tubular shield 58 is disposed in covering relation over the coiled heat exchange portion 32 of each plugging unit 10, the condensation of temperature-sustaining vapor within the manifold 12 is materially reduced during operation of any one of the plugging units 10, because as soon as condensate forms and is trapped within the shield 58 at the spiral void resulting from the coiled form of the heat exchange portion 32, the trapped condensate acts as a barrier preventing further access of vapor to the coiled portion 32 for condensation thereat. The significance of this feature is in eliminating false demands for manifold heat from sensors located in the manifold near enough to a particular plugging unit 10 to be locally affected when the unit is placed in operation if it is not externally shielded.

Also, mechanical purchase on a solidified polymer plug can be provided by deforming the distribution conduit 16 at the installed heat exchange portion 32 of the plugging unit 10 so as to vary its cross sectional configuration. A simple way of acomplishing this result is to flatten the distribution conduit 16 adjacently downstream of the heat exchange portion 32 as indicated at 16 in FIGS. 4 and 5. A cylindrical polymer plug solidified at the heat exchange portion 32 will thus be mechanically obstructed and held by the deformed conduit portion 16' until it is allowed to remelt, while normal flow of melted polymer will not be appreciably affected. Such an arrangement can be employed effectively whenever the spinning system involved operates with a polymer feeding pressure high enough to make it difficult to hold a polymer plug in place by friction alone.

As to cooling fluids, water has been successfully used in operating the plugging means of the present invention, although if the water supply available is at all rich in minerals it should be subjected to a softening treatment before use to avoid any build-up of mineral deposits in the heat exchange structures from the water flashing that occurs during operation of the plugging units. If distilled water is available, an alternative is to employ it in a closed system that maintains all of the plugging units permanetly connected for selective recirculation of the distilled water as they are operated. Another option is the use of a liquid agent as the cooling fluid that leaves no residue upon vaporizing, such as a polyalkylene glycol. Also, air or other gaseous agents could be employed as the cooling fluid. With any cooling fluid that is selected it is desirable to provide a pressure switch at the supply source arranged to sense the supply pressure during use of any plugging unit and to shut down the entire spinning system in the event of a pressure drop below that required to maintain the plugging unit operating effectively.

The present invention has been described in detail above for purposes of illustration only and is not intended to be limited by this description or otherwise to exclude any variation or equivalent embodiment that would be apparent from, or reasonably suggested by, the foregoing disclosure to the skill of the art.

What We claim is:

1. In a melt system having a pressure-fed inlet for melted polymer from which a plurality of polymer distribution conduits, housed within a manifold heated by circulation therethrough of a temperature-sustaining vapor, run to respective metering pumps that deliver in turn to polymer extrusion outlets, the improvement which comprises a plugging unit included in said melt system for each of said polymer distribution conduits, each of said plugging units incorporating a heat exchange structure installed within said heated manifold on the related polymer distribution conduit at a position within the temperaturesustaining influence of said circulated vapor and upstream of the associated metering pump and means accessible externally of said manifold for selectively connecting any one of said heat exchange structures for circulation of cooling fluid therethrough whereby cooling fluid can be applied through any one of said plugging units to solidify polymer temporairly in the related distribution conduit and thereby plug the same so that the associated pump may be disconnected and replaced whenever necessary without interrupting operation at the other conduits, While allowing operation to resume in due course at the replaced pump and related conduit simply by stopping the circulation of cooling fluid.

2. In a melt system, the improvement defined in claim 1 and further characterized in that said system is adapted for melt spinnning and incorporates spinnerettes as the polymer extrusion outlets.

3. In a melt system, the improvement defined in claim 1 and further characterized in that said heat exchange structure is formed by a coiled disposition of tubing about the related distribution conduit.

4. In a melt system, the improvement defined in claim 3 and further characterized in that said heat exchange structure additionally includes a tubular shield covering the coiled tubing throughout its length.

5. In a melt system, the improvement defined in claim 1 and further characterized in that a portion of said distribution conduits at the installed heat exchange structure of said plugging units is deformed to vary the cross sectional configuration of the conduits thereat for mechanically holding solidified polymer against melted polymer feeding pressure thereon.

6. In a melt system, the improvement defined in claim 5 and further characterized in that the deformed portion of said distribution conduits is arranged adjacently downstream of the installed heat exchange structure of said plugging units.

References Cited UNITED STATES PATENTS 2,707,306 5/1955 Neber et a1. 18-8 A 2,841,821 7/1958 Phipps 18-8 A 3,041,048 6/1962 Heijnis 18-8 A X FOREIGN PATENTS 7,382 4/1969 Japan 264-176 F J. SPENCER OVERHOLSER, Primary Examiner M. O. SUTTON, Assistant Examiner US. Cl. X111. 264-176 F 

